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<a name="Diagnostic-Pragmas"></a>
<div class="header">
<p>
Next: <a href="Visibility-Pragmas.html#Visibility-Pragmas" accesskey="n" rel="next">Visibility Pragmas</a>, Previous: <a href="Weak-Pragmas.html#Weak-Pragmas" accesskey="p" rel="prev">Weak Pragmas</a>, Up: <a href="Pragmas.html#Pragmas" accesskey="u" rel="up">Pragmas</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Indices.html#Indices" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="Diagnostic-Pragmas-1"></a>
<h4 class="subsection">6.62.12 Diagnostic Pragmas</h4>

<p>GCC allows the user to selectively enable or disable certain types of
diagnostics, and change the kind of the diagnostic.  For example, a
project&rsquo;s policy might require that all sources compile with
<samp>-Werror</samp> but certain files might have exceptions allowing
specific types of warnings.  Or, a project might selectively enable
diagnostics and treat them as errors depending on which preprocessor
macros are defined.
</p>
<dl compact="compact">
<dd><a name="index-pragma_002c-diagnostic"></a>
</dd>
<dt><code>#pragma GCC diagnostic <var>kind</var> <var>option</var></code></dt>
<dd>
<p>Modifies the disposition of a diagnostic.  Note that not all
diagnostics are modifiable; at the moment only warnings (normally
controlled by &lsquo;<samp>-W&hellip;</samp>&rsquo;) can be controlled, and not all of them.
Use <samp>-fdiagnostics-show-option</samp> to determine which diagnostics
are controllable and which option controls them.
</p>
<p><var>kind</var> is &lsquo;<samp>error</samp>&rsquo; to treat this diagnostic as an error,
&lsquo;<samp>warning</samp>&rsquo; to treat it like a warning (even if <samp>-Werror</samp> is
in effect), or &lsquo;<samp>ignored</samp>&rsquo; if the diagnostic is to be ignored.
<var>option</var> is a double quoted string that matches the command-line
option.
</p>
<div class="smallexample">
<pre class="smallexample">#pragma GCC diagnostic warning &quot;-Wformat&quot;
#pragma GCC diagnostic error &quot;-Wformat&quot;
#pragma GCC diagnostic ignored &quot;-Wformat&quot;
</pre></div>

<p>Note that these pragmas override any command-line options.  GCC keeps
track of the location of each pragma, and issues diagnostics according
to the state as of that point in the source file.  Thus, pragmas occurring
after a line do not affect diagnostics caused by that line.
</p>
</dd>
<dt><code>#pragma GCC diagnostic push</code></dt>
<dt><code>#pragma GCC diagnostic pop</code></dt>
<dd>
<p>Causes GCC to remember the state of the diagnostics as of each
<code>push</code>, and restore to that point at each <code>pop</code>.  If a
<code>pop</code> has no matching <code>push</code>, the command-line options are
restored.
</p>
<div class="smallexample">
<pre class="smallexample">#pragma GCC diagnostic error &quot;-Wuninitialized&quot;
  foo(a);                       /* error is given for this one */
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored &quot;-Wuninitialized&quot;
  foo(b);                       /* no diagnostic for this one */
#pragma GCC diagnostic pop
  foo(c);                       /* error is given for this one */
#pragma GCC diagnostic pop
  foo(d);                       /* depends on command-line options */
</pre></div>

</dd>
<dt><code>#pragma GCC diagnostic ignored_attributes</code></dt>
<dd>
<p>Similarly to <samp>-Wno-attributes=</samp>, this pragma allows users to suppress
warnings about unknown scoped attributes (in C++11 and C2X).  For example,
<code>#pragma GCC diagnostic ignored_attributes &quot;vendor::attr&quot;</code> disables
warning about the following declaration:
</p>
<div class="smallexample">
<pre class="smallexample">[[vendor::attr]] void f();
</pre></div>

<p>whereas <code>#pragma GCC diagnostic ignored_attributes &quot;vendor::&quot;</code> prevents
warning about both of these declarations:
</p>
<div class="smallexample">
<pre class="smallexample">[[vendor::safe]] void f();
[[vendor::unsafe]] void f2();
</pre></div>

</dd>
</dl>

<p>GCC also offers a simple mechanism for printing messages during
compilation.
</p>
<dl compact="compact">
<dd><a name="index-pragma_002c-diagnostic-1"></a>
</dd>
<dt><code>#pragma message <var>string</var></code></dt>
<dd>
<p>Prints <var>string</var> as a compiler message on compilation.  The message
is informational only, and is neither a compilation warning nor an
error.  Newlines can be included in the string by using the &lsquo;<samp>\n</samp>&rsquo;
escape sequence.
</p>
<div class="smallexample">
<pre class="smallexample">#pragma message &quot;Compiling &quot; __FILE__ &quot;...&quot;
</pre></div>

<p><var>string</var> may be parenthesized, and is printed with location
information.  For example,
</p>
<div class="smallexample">
<pre class="smallexample">#define DO_PRAGMA(x) _Pragma (#x)
#define TODO(x) DO_PRAGMA(message (&quot;TODO - &quot; #x))

TODO(Remember to fix this)
</pre></div>

<p>prints &lsquo;<samp>/tmp/file.c:4: note: #pragma message:
TODO - Remember to fix this</samp>&rsquo;.
</p>
<a name="index-pragma_002c-diagnostic-2"></a>
</dd>
<dt><code>#pragma GCC error <var>message</var></code></dt>
<dd><p>Generates an error message.  This pragma <em>is</em> considered to
indicate an error in the compilation, and it will be treated as such.
</p>
<p>Newlines can be included in the string by using the &lsquo;<samp>\n</samp>&rsquo;
escape sequence.  They will be displayed as newlines even if the
<samp>-fmessage-length</samp> option is set to zero.
</p>
<p>The error is only generated if the pragma is present in the code after
pre-processing has been completed.  It does not matter however if the
code containing the pragma is unreachable:
</p>
<div class="smallexample">
<pre class="smallexample">#if 0
#pragma GCC error &quot;this error is not seen&quot;
#endif
void foo (void)
{
  return;
#pragma GCC error &quot;this error is seen&quot;
}
</pre></div>

<a name="index-pragma_002c-diagnostic-3"></a>
</dd>
<dt><code>#pragma GCC warning <var>message</var></code></dt>
<dd><p>This is just like &lsquo;<samp>pragma GCC error</samp>&rsquo; except that a warning
message is issued instead of an error message.  Unless
<samp>-Werror</samp> is in effect, in which case this pragma will generate
an error as well.
</p>
</dd>
</dl>

<hr>
<div class="header">
<p>
Next: <a href="Visibility-Pragmas.html#Visibility-Pragmas" accesskey="n" rel="next">Visibility Pragmas</a>, Previous: <a href="Weak-Pragmas.html#Weak-Pragmas" accesskey="p" rel="prev">Weak Pragmas</a>, Up: <a href="Pragmas.html#Pragmas" accesskey="u" rel="up">Pragmas</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Indices.html#Indices" title="Index" rel="index">Index</a>]</p>
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